Digging into the CTC-9

[zenithfan1]

Originally Posted by andy

After the reports of implosions we have seen, I wouldn't even consider running a set without a safety glass. If something hits the screen just right, or the clamps are a little too tight, it could send glass everywhere.

No worries, it's not in use. It's in storage right now. I fianally found a flyback for it this year at the ETF convention. I'm going to restore it soon, and install safety glass

[zenithfan1]

I'll study the schematic later tonight after the kids go to bed, it's nuts around here right now. I'll compare it to what's in the set to determine exactly what has been changed for the CRT.

[zenithfan1]

According to the RCA Field Service Guide, the Hv should be 22.5Kv. That would be with brightness and contrast at minimum. I'll post a pic of my screen and grid connections as soon as the camera charges . Then you can compare it to yours.

[leadlike]

Thanks-

I set it at 24kv, making the flyback a little warm after a couple hours of running. I have yet to adjust the flyback current. The schematic claims there is a fixture on the chassis for attaching your meter to while doing this adjustment-not sure where that is supposed to be.

I made up some crummy line art in paint and burned it to dvd-grids, horizontal lines, dots, etc. I did a bit of a convergence setup, but not surprisingly, it is a serious pain to do. I don't think I am getting any response out of the 3 slug coils on the board at all.

With the guidelines on establishing color balance, I adjusted for best picture while keeping G2 low. This has produced a magnificent picture,though there is still the occasional scene where I want to crawl back to the chassis and turn down the green a bit more. Where before the set only had a watchable picture with brightness and contrast all the way up, All of the controls are more or less in the middle position. If it weren't for fear of burning up the flyback (ie getting hv dialed in right) and having the convergence properly done, I'd say this thing was looking really good.

[peverett]

I have some early 1950s Hoffman B&W sets. The safety glass on these is true safety glass with the embedded plastic layer.

[zenithfan1]

The only difference I see from original is the yellow/blue stripe and yellow/green stripe wires (pin 13 and 5 hooked together) move from the original position on the 2.7k ohm resistor (R71) to the 1.8k ohm (R70), they are now connected to the extreme end by the video output board where the peaking coil is. The yellow/red remains connected to R69 as per the schematic. see pics. I'm not an expert on this mod so if anyone else knows something, please chime in. I'm just going by what was done to my set, the picture tube was changed by the RCA service company so I assume it is correct. The tube was installed 4/15/68 and is still going strong.


edit: I'm not sure my set is right, so I took down the pictures.

[jr_tech]

Originally Posted by peverett

I have some early 1950s Hoffman B&W sets. The safety glass on these is true safety glass with the embedded plastic layer.

Ditto on a late 40s RCA that I checked. The safety glass on my '53 Philco does not have the embedded (PVB?) layer, but is nearly 1/4" thick and appears that it could be tempered... pretty strong hunk of glass.
How thick are the curved shields that have been removed from the bonded color CRTs ?

jr

[zenithfan1]

They are not as thick as the ones on the un-bonded 21FBP22. It would be great to find one with a gasket from an un-bonded tube to put on the FJP when necessary. I have a tinted unfrosted one but it's scratched in the middle. I wish I could come across a few that are clear and unfrosted.

[zenithfan1]

There was a lot more to it than I thought, everything you need to know is right here. Thank you Steve D. I found this while digging in my files tonight. I'm glad I found it, I forgot it was there.

[fsjonsey]

Holy Crap. I'm glad you are both okay.

Has anyone tried soaking a CRT in a vat of a relatively cheap petroleum solvent like kerosene or Diesel? I'd imagine that kerosene would dissolve PVA.
I've thought about doing a test on some PVA removed from an old CRT. Cutting up the old PVA into small pieces and seeing how it reacted to different solvents. If anyone has saved some old PVA, I'd be glad to do it.

[leadlike]

Wow! Lots of mods to do! I'm not sure if all of them were done or not, but one of my complaints about the picture was that the reds were really too strong, with pink highlights on more intense reds. I'll be out of town the rest of the weekend, and then another order from Mouser

Before I forget, I would like to replace the selenium triple rectifier with three diodes on the convergence board-are they of any special type?

[zenithfan1]

I was looking at the book I posted and what was done to my set is not the same as what is described in the book. I would go by what's in the book if I were you, not my set. I'm going to look into what was done to mine and see if I can make sense of it. The book says to move the red cathode wire to the position of blue and green, mine has the blue and green moved to the red. Arrrgh.... I'd better look at the other stuff too, it does say that with a sulfide tube, it is not necessary to do the pink highlight mod. Any CTC 9 gurus out there wanna chime in?

As for those diodes, I think they are pretty vanilla. 1N4007 comes to mind.

[Phil Nelson]

Originally Posted by leadlike

replace the selenium triple rectifier with three diodes on the convergence board-are they of any special type?

When I replaced the rectifier on my CTC-11 board, I got two opinions.

One guy said he used "ordinary power supply diodes," which I took to mean 1N4007.

Another said those are too slow and sent me some "fast slew" diodes (his term) which I installed. Hard to read the type number when they are installed, but it may be 1937. At least, the last three digits are 937.

If you have a bunch of 1N4007 lying around, you could try those and see what happens. Pretty cheap experiment as long as you don't fry the board.

Phil Nelson

[jeyurkon]

Originally Posted by Phil Nelson

When I replaced the rectifier on my CTC-11 board, I got two opinions.

One guy said he used "ordinary power supply diodes," which I took to mean 1N4007.

Another said those are too slow and sent me some "fast slew" diodes (his term) which I installed. Hard to read the type number when they are installed, but it may be 1937. At least, the last three digits are 937.

If you have a bunch of 1N4007 lying around, you could try those and see what happens. Pretty cheap experiment as long as you don't fry the board.

Phil Nelson

Guess he meant "fast recovery." Any chance those are 1N4937's?

John

[Phil Nelson]

That might be the number. They're close to the board, but using a little dental mirror, the part I can read looks more like 4937 than 1937.

Phil